Coating process



Patented Dec. 5, 193

V UNITED STATES PATENT OFFICE COATING raocrzss Oliflord Jay Rolle, Yonkers, N. Y., assignor to Interchcmlcal Corpor tion, New York, N. Y., a corporation of Ohio No Drawing. Application August 28, 1936, Serial No. 98,337

3 Claims. (01. 113-120) This invention relates to the manufacture of Prior to e S ap g of the metal articles, it coated metal articles, and more particularly to Should be capable of lubricating the Surface, 88 the manufacture of tin cans lined with two or Well as tending to form a o uous film where more thin coats of resin compositions or the like. applied, 50 85 to minimize -8e to the under- The purpose of lining cans or metal food conco y he i r machinery ployed to bend l tainers is, of course, to form a durable,"impermcthe metal t the desired p and it Should able coating which will prevent the ,contents of be able o Withstand e high pe atu es dethe containers from coming in contact with the veloped incident t he repeated operation of metal. When the lining consists ,of more than these dies- 10 one coat, the top-coat should bond ith the I have found that excellent results are obtain- 10 t able by coating the article, applying to the coated In making multi-coated containers, it is often su ace a c pos t n con a in a small propo deslrable to apply the first coat, th n b d the tion of non-volatile plasticizer which is water coated metal into the desired shape, and therep l and t apply g a resin composition after apply the top-coat, In shaping th t which is compatible with the plasticizer. Accord- 18 the dies and other machinery tend to damage the ing to the pre er ed p a my ve t on. the applied coating, which is fragile. nonvolatile plasticlzer is employed in the form A feature of the present invention accordingly 0f Weteremlllsien, in which t Water constiresides in the provision of a coating process intilteS the external Phase of the emulsion, the

20 volving the application to the under-coat, before emulsion being sufficiently stable r use as a go the top-coat is applied, of a preparation which lubricant, d y Permitting e po ation of the cooperates in the production of' a u e i ne mwater prior to the application of the over-coat. posite coating, and which is also capable of servore p fi y, the e 0 8 first p e ing as a lubricant, for preventing damage to the to the article to be coated, and the film formed under-coat, when the metal is formed or shaped is allowed to set to a condition in which it is no subsequent to the application of the under-coat. longer fluid. 7 Normally, it is' baked and inthe I have, found that th preparation which is case of some under-coats theresin is converted applied to the under-coat, for'present purposes, to the C st g e there is pp to must satisfy a number of varied and seemingly sprayed upon the coated surface a small quantity 3 conflicting requirements. For one thing, it must of an emulsion containing a y cop c, be a non-solvent, or have very limited solvent water-immiscible pias i r, which is miscible power, for the under-coat, so that it does not with the composition of the over-coat, and which impair the latter; it must permit the over-coat preferably has some solvent power for the resin to adhere firmly to the under-coat, and assist in' of this composition, the water being next allowed producing a uniform spread and flow of the overto evaporate from the emulsion. The emulsifycoating composition; it should wet the surface ing agent employed preferably evaporates with to which the top-coat is applied, so that the surthe water. Heat may be applied, if desired, to face receives a uniform amount of composition expedite the evaporation of the water, and this tending to form a continuous thin film; and any heat" may be provided by the dies which form portions of the preparation which remain on the the metal, when the article is shaped after the first coat when the second coat is applied must application of the under-coat. Thereupon, tlie be such that they do not cause blistering of the over-coat may be directly applied to the undercomposite film when the coated article is baked coat on the surface of which the plasticizer reto harden the resins. Moreover, the preparation mains, without the need for removal of the latter,

5 which is applied between the films should not be and with the advantage of securing a superior excessively viscous or thick, and should not have composite coating. The coated article may then a tendency to unbalance the formula of the topbe again baked. coat. On the other hand, the preparation should By way of a specific example illustrating my be miscible with the composition of the top-coa't'. invention,there may first be applied to the sur- It is also important that the preparation should face to be coated, a resin composition of the 50 be non-hygroscopic, for free water injures the type disclosed in co-pending application of Frishtop-coat. And it is also highly desirable that korn and Wahl, Serial No. 35,066, filed August 7, the composition be inexpensive, and easy to apply. 1935, and disclosing a mixture of an oil-free,

When the preparation must also serve as a phenol-formaldehyde resin which is insolubilizalubricant, i. e., when the under-coat is applied ble by heat, an alkyd resin plasticizer such as a "GlyptaP resin made by General Electric Company, and suitable solvents. However, other similar compositions may be employed, and indeed lacquers and the like may be substituted for the resin film in some cases.

A satisfactory composition or lubricant for application to the under-coat includes the following ingredients:

Parts by volume Water repellent plasticizer (butyl cellosolve stearate) 32 Emulsifier (morpholine) 1 Water 95 However, various other plasticizers, such as trii ethanolamine oleate, butyl cellosolve phthalate.

and butyl phthalyl butyl glycolate, having the characteristics mentioned, may be used. It is advantageous that the plasticizer have a surface tension which is less than about 40 dynes per square centimeter, and preferably in the order of to 35 dynes per square centimeter. In other Words, the lubricant composition should have a surface tension such that it tends to form a.

continuous film on those portions of the surface to which it is applied. In order to produce a stable emulsion, it is advantageous that the specific gravity of the plasticizer be less than, or not markedly greater than, the specific gravity of water. I prefer to employ a plasticizer having a specific gravity of less than about 1.1. Other emulsifiers may be employed, and the mixture may be diluted with as much as seven volumes of water per volume of the above composition.

The coated metal, treated with a lubricant of this character, if it has not previously been bent to shape, may now be fed to the dies which form or shape it. As mentioned, these dies generate considerable heat, and this heat serves to partially or wholly vaporize the water from the emulsion. I

. The top-coat may next be applied to the article,

without the need for removing the lubricant from the surface of the under-coat. An excellent formula for the top-coat is as follows:

vinyloid H. is a vinyl resin which is understood to be produced by polymerization of vinyl compounds such as vinyl acetate and vinyl. chloride. While I have found that particularly satisfactory results are obtainable with the use of phenol formaldehyde resins in the under-coat and vinyloid resins in the top-coat, the invention in its broader aspects is not restricted to the use of different types of resins in the different coats.

The terms and expressions which have been employed are used'as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described, or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed.

What I claim is:

1. The method of making an article coated with a resin composition, which comprises applying to a surface of the article an emulsion containing a resin plasticizer which is miscible and compatible with said resin composition, and a volatile liquid which constitutes the external phase of said emulsion, bending said article while furnishing heat thereto, thereby vaporizingsaid liquid, and applying said resin composition to the surface on which said plasticizer remains.

2. In a method of manufacturing multi-coated metal articles, such as tin cans, the steps which comprise lubricating a coated blank, prior to the application of the overcoat, with an aqueous liquid containing a small proportion of a nonvolatile plasticizer which is compatible with the compositionof the overcoat, shaping the blank under the lubricating action of said liquid and with the application of heat to the blank, thereby to evaporate the water and leave the non-volatile plasticizer, and subsequently applying the overcoat While the plasticizer remains on the blank.

3. In the method of manufacturing multicoated metal articles, such as tin cans, the steps which comprise lubricating a coated blank, prior to the application-of the overcoat, with an aqueous emulsion having, the water in the external phase and containing a small proportion of a non-volatile plasticizer which is compatible with the composition of the overcoat, shaping the blank under the lubricating action of said liquid and with the application of heat to the blank, thereby to evaporate the water and, leave the nonvolatile plasticizer, and subsequently applying the overcoat while the plasticizer remains on the blank. 1

CLIFFORD JAY ROLLE. 

